German Ostpreussen
Historical region and former Prussian province, east of Pomerania .
From 1815 it was known as East Prussia, part of the kingdom of Prussia , and in the 19th century it was a stronghold of Prussian Junkers, a military aristocracy. It was the scene of successful resistance against the Russians in World War I. Following the war, it was separated from the rest of Germany by the Polish Corridor (1919); it was reunited with the Reich by the German conquest of Poland in 1939. Between World War I and World War II, it was bounded to the north by the Baltic Sea, east by Lithuania, and south and west by Poland and the free city of Danzig (now Gdańsk, Pol.). Overrun by Soviet armies at the end of World War II, in 1945 it was divided between the Soviet Union and Poland.